This invention relates generally to the field of performing downhole functions in a well, and is particularly applicable to downhole well completion tools.
In completing a product recovery well, such as in the oil and gas industry, several downhole tasks or functions must generally be performed with tools lowered through the well pipe or casing. These tools may include, depending on the required tasks to be performed, perforating guns that ballistically produce holes in the well pipe wall to enable access to a target formation, bridge plug tools that install sealing plugs at a desired depth within the pipe, packer-setting tools that create a temporary seal about the tool and valves that are opened or closed.
Sometimes these tools are electrically operated and are lowered on a wireline, configured as a string of tools. Alternatively, the tools are tubing-conveyed, e.g. lowered into the well bore on the end of multiple joints of tubing or a long metal tube or pipe from a coil, and activated by pressurizing the interior of the tubing. Sometimes the tools are lowered on cables and activated by pressurizing the interior of the well pipe or casing. Other systems have also been employed.
Typically, ballistic tools are not "armed" (i.e., not yet configured to fire upon receipt of a hydraulic or electric stimulus) until just before being placed in the well, in order to avoid accidental firings at surface. Once armed, very high safety standards must be maintained to avoid potentially deadly premature firings until the tool is safely below ground. Even after the armed tool has been lowered into the well, an accidental, premature firing can result in costly well damage.